The invention relates to the field of planar antenna devices, and especially to a planar antenna device including a conductive first plate acting as a ground plane, a second conductive plate and a grounding means connecting the second conducting plate and the ground plane. Specifically, it relates to an aperture-coupled planar antenna device for a mobile radio communication device, e.g., a hand-portable telephone. The invention further relates to this type of antenna which is intended for operation within two separated frequency bands.